A construction machine, such as an excavator and a wheel loader, generally includes a hydraulic pump driven by an engine, and a hydraulic system for driving a plurality or working machines, such as a boom, an arm, a bucket, a travel motor, and a turning motor, through pressure of working oil discharged from the hydraulic pump.
The hydraulic pump used in the hydraulic system for the construction machine is a variable capacity type pump including a swash plate formed inside the pump and an adjusting device for adjusting a swash plate angle (swash plate angle), and particularly, may be divided into a machine control type or an electronic control type according to a type of an instruction input to the adjusting device in order to adjust the swash plate angle.
The initial hydraulic pump mainly employs the machine control method, but the electronic control type for controlling the swash plate angle by applying an electric signal to the adjusting device has been introduced today. The hydraulic pump of the electronic control type includes a so-called pressure control type electric hydraulic pump.
The pressure control type electric hydraulic pump is controlled by a control means, such as an electronic control unit. The electronic control unit receives an operative amount of a joystick according to an operation of a lever, such as a joystick within an operation seat of the construction machine and a value of a swash plate angle from a sensor mounted inside the electronic hydraulic pump as electric signals, respectively, and outputs the electric signal for controlling the pressure to the corresponding electronic hydraulic pump.
However, in a case of the construction machine using the electronic hydraulic pump, when the electronic control unit fails to be operated, for example, when an operation signal (the operative amount) of the joystick, which is input to the electronic control unit, is not normally input, there may occur a problem in that the electronic control unit is not able to normally control the electronic hydraulic pump.
As described above, when the construction machine is controlled, the electronic control unit may arbitrarily intend to maintain a uniform pump pressure even when an operation signal input to the electronic control unit is abnormal, thereby leading to problems such as an increase in noise of equipment, for example, the pump, of the construction machine, a decrease in durability of hydraulic components, such as the hydraulic pump or a valve, and an increase in fuel consumption and a decrease in durability of an engine due to maintenance of the engine in a continuous high load state.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.